of the Doctor Who theme song. The day before this episode was broadcast in the UK on Disney XD, another K-9 (K-9 Mark IV) appeared with the Tenth Doctor in The Wedding of Sarah Jane Smith on CBBC on BBC One. Professor Gryffen's laboratory & home is in a disused police station which still bears the exterior appearance of its former purpose (police lamp next to the front door, signage, inter alia); the building is shown in "The Cambridge Spy" to have been an active police station as recently as 23 November 1963. This parallels the TARDIS' exterior appearance as a 1963 police box. External links K9 Official The Doctor Who Site K-9 (TV series) episodes 2009 British television episodes